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A new class of phenalenyl-based neutral radical molecular conductors has recently been reported; a distinctive feature of these molecular solids is the absence of the well-defined conducting pathway(s) that are characteristic of the organic charge- transfer salts. These radicals do not stack in the solid state, and the requisite carbon- carbon contacts are all larger than the sum of the van der Waals distances. Magnetic susceptibility measurements show that these compounds usually exist as isolated free radicals with one spin per molecule (at least over some temperature range), apparently supporting the idea that there is little interaction between the molecules in the solid state. Nevertheless, these radicals show the highest conductivity (RT 0.05 S/cm) of any neutral organic solid and the conduction mechanism is at present unresolved. In this article we report a structurally related radical with a resistivity five orders of magnitude higher than that of the previously reported radicals. We analyze the crystallographic and electronic structure of this solid in detail and point out some of the challenges that remain in relating structure, magnetism, and conductivity in this new class of organic solids. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 95: 853- 865, 2003

Increasing net patient revenues from teaching clinics is one of the alternatives available to dental schools seeking to alleviate economic pressures. Managerial decisions directed to this end require accurate and useful data on clinic finances and economic organization. An important step in this direction can be taken by defining the teaching clinic as a cost center, that is as an economic entity in a dental school with identifiable specific resources, costs, and revenues. This paper describes the accounting and economics frameworks within which resources and costs are classified and allocated into direct and indirect, and fixed and variable categories. The development and structure of a cost-revenue model designed for the teaching clinics at the University of Connecticut School of Dental Medicine is described to illustrate an application of the cost center concept.

The title molecule, 3,7-bis(2-thienyl)-1,5,2,4,6,8-dithiatetrazocine, C 10 H 6 N 4 S 4 , is planar within 0.069 (5) A and crystallizes in the monoclinic space group P2 1 /c. There are two centrosymmetric molecules in the cell; these are stacked such that each eight-membered C 2 N 4 S 2 ring has a thienyl ring above and below it. The mean interplanar separation is 3.55 (2) A.

The present paper deals with the microstructural parameters calculated from X-ray diffraction data, electrical and optical investigations, and scanning tunneling microscopy (STM) studies on ZnIn2S4 IIIa layer type CdIn2S4-xSex (1.75 ≤ x ≤ 2.75) quaternary chalcogenides. Microstructural parameters such as dislocation density, root-mean-square strain, stacking fault probability, crystallite size anisotropy, and layer disorder parameters of these compounds have been calculated. The temperature variation of electrical conductivity (25−400 °C) confirmed semiconducting behavior. The band gaps of all these compounds obtained from STM and optical measurements are in the range 1.57−1.77 eV and are comparable to each other irrespective of the technique used.

C 24 H 20 ClN 3 P 2 Se cristallise dans P1 avec a=9,759, b=11,046, c=13,332 A, α=65,50, β=64,89, γ=74,96 o , Z=2; affinement jusqu'a R=0,036. Dans le cycle a 5 chai←nons, l'un des liens entre P et N est presque plan (a 0,053 A pres), tandis que l'atome Se soit de ce plan de 0,499 A du cote du chlore. Les longueurs des liaisons de la sequence Se−N−P−N sont en moyenne de 1,730; 1,637 et 1,584 A. Les angles des liaisons du cycle autour des atomes Se et P sont respectivement de 111,5 o et 117,8 o

Phenothiazine-10-propionitrile, C12H8SNC2H4CN, crystallizes in the centrosymmetric monoclinic space group P21/n, with a = 5.785(1)A, b = 15.427(3)A, c = 14.497(4)A, β = 92.50(1)°, Z = 4, Dmeas = 1.29(1) g cm3 and Dcalc = 1.28 g cm3 at 23°. Three dimensional X-ray data were collected with a manual diffractometer using MoKα (λ 0.71069A) radiation and by multiple film Weissenberg techniques using CuKα (λ 1.5418A) radiation. The structure was determined by Patterson and Fourier methods and refined with 519 observed reflections by full matrix least-squares methods to an R of 0.077. The dihedral angle between the two planes of the o-phenylene rings is 135.4(3)°. In the folded heterocyclic ring the C-S-C angle is 97.8(7)° and the average CS bond is 1.76(1)A. A comparison of this structure to that of phenothiazine-10-propionic acid shows the two chemically similar molecules have the same dihedral angles in spite of completely different solid state packing patterns.

The crystal structure of phenothiazine-10-propionic acid, C12H8SNC2H4COOH, was determined from three-dimensional X-ray diffraction data collected with a manual diffractomer using MoKα (λ 0.71069 A) radiation. The space group is P21/c with a = 7.888 (2)A, b = 8.703 (2)A, c = 19.700 (8)A, β = 101.42 (1)°, Z = 4, Dmeas = 1.35(2) g. cm−3 and Dcalc = 1.36 g. cm−3 at 23°. The structure was determined by the direct method and refined with 500 observed reflections by full-matrix least squares to an R of 0.072. The molecule is folded along the S-N axis and the dihedral angle is 136.5°. The C-S-C angle is 98.5(7)° and the average C-S bond is 1.77(2)A. The shortening of the C-S bond, the small value of the C-S-C angle and the folding of the molecule are typical of the phenothiazine class of compounds and are assumed to be due to sulfur d orbital participation in ring bonding.

The structure of 2-(trifluoromethyl)phenothiazine, C13H8NSF3, was determined by single crystal X-ray diffraction. The molecule crystallizes in space group P212121, with a = 7.766(2), b = 5.957(1), and c = 23.499(5)A. The final R value is 0.073. The CSC bond angle is 102.0°, the CNC bond angle is 124.8°, and the dihedral angle between the phenylene planes is 171.2(1)°. The hydrogen atom bonded to the nitrogen atom was located; it is on the inside of the butterfly angle and the S…NH bond angle is 173.3°.

The oxidation of the cofacial dimer (I), which is in equilibrium with its remarkably stable radical (II), with nitrosonium salts yields the corresponding salts (III).

Cristallisation dans le groupe P2 1 /c avec a=9,216, b=14,318 et c=10,229 A, β=104,57°, Z=4. Affinement jusqu'a R=0,037. La molecule est formee d'une unite norbornenyl avec deux groupes S 3 N attaches de facon exo aux positions 2,3. Effets des differents substituants sur l'energie de transition π*→π* des derives X-S 3 N

A study of the synthesis and structure of dibenzometallacyclohexa-2,5-dienes incorporating titanium, hafnium, and cobalt is reported. The crystal structures of the titanacycle and cobaltacycle exhibit boat conformations. Variable-temperature 1 H NMR data implicate fast-exchange spectra for boat-boat interconversion in the titanacycle and hafnacycle

The oxidation of the S/sub 3/N/sub 3//sup -/ ion in acetonitrile solution by molecular oxygen gives rise to four major products: S/sub 4/N/sub 5//sup -/, S/sub 4/N/sub 5/O/sup -/, S/sub 3/N/sub 3/O/sup -/, and S/sub 3/N/sub 3/O/sub 2//sup -/. The relative yields of these species are a function of the flow rate of oxygen, and the progress of the reaction and the structure of the various ions in solution can be analyzed by using /sup 15/N NMR spectroscopy. The crystal and molecular structures of (Ph/sub 3/P)/sub 2/N/sup +/S/sub 3/N/sub 3/O/sup -/ and (Ph/sub 3/P)/sub 2/N/sup +/S/sub 3/N/sub 2/O/sub 2//sup -/ have been determined by x-ray diffraction. Crystals of the former are monoclinic, space group P2/sub 1//c, with a = 17.161 (2) A, b = 9.970 (1) A, c = 20.591 (2) A, ..beta.. = 104.45 (1)/sup 0/, V = 3411.7 A/sup 3/, and Z = 4. Crystals of the latter are monoclinic, space group P2/sub 1/, with a = 12.421 (1) A, b = 13.036 (1) A, c = 10.699 (1) A, ..beta.. = 103.36 (1)/sup 0/, V = 1685.6 A/sup 3/, and Z = 2. Both structures were solved by direct methods and refined by full-matrix least-squares procedures; formore » (Ph/sub 3/P)/sub 2/N/sup +/S/sub 3/N/sub 3/O/sup -/ the final R = 0.053 and R/sub w/ = 0.075 for 3058 reflections with I > 3sigma(I), and for (Ph/sub 3/P)/sub 2/N/sup +/S/sub 3/N/sub 3/O/sub 2//sup -/ the final R = 0.048 and R/sub w/ = 0.057 for 2312 reflections with I > 3sigma(I). The two anions S/sub 3/N/sub 3/O/sup -/ and S/sub 3/N/sub 3/O/sub 2//sup -/ both possess six-membered S/sub 3/N/sub 3/ ring structures with exocyclic oxygen atoms bonded to sulfur (in S/sub 3/N/sub 3/O/sub 2//sup -/ the oxygens are geminally substituted). Both rings exhibit significant variations in chemically equivalent bond lengths and angles. The visible spectra of S/sub 3/N/sub 3/O/sup -/ (lambda/sub max/ = 509 and 340 nm) and S/sub 3/N/sub 3/O/sub 2//sup -/ (lambda/sub max/ = 562 and 362 nm) are interpreted in terms of the expected perturbations on the ..pi..-manifold of the S/sub 3/N/sub 3//sup -/ anion; the observed absorptions are assigned to ..pi..* ..-->.. ..pi..* type excitations. 34 references, 5 figures, 6 tables.« less